Important Average Questions-SSC CGL

1. The average age of 30 boys of a class is 14 years. When age of class teacher is included, average becomes 15 years. Find Age of teacher.

Solution: If age of teacher was 14 years, average would remain same i.e. 14 years.

But average increased by 1 year, that means that teacher contributed 1 year to all i.e. 30+1=31

So age of teacher = 14+31=45 years.

2. In a class, average age of 24 boys and one teacher was 15 years. If age of teacher is removed, average remains 14. Find the age of teacher.

Solution: 15+24\times 1 = 39 years

3. Average weight of 4 men is increased by 3 kg when one of them whose weighs 120 kg is replaced by another man. Find the age of that new person.

Solution: 120+4\times3 = 132 kg

4. A batsman scored 87 runs in 17th innings and therefore, his run-rate increased by 3 runs per match. Find his new run-rate.

Solution: 17 \times 3 =51 is distributed over all innings.

Remaining 87-51=36 was his old run rate.

And new run rate = 36+3 = 39.

5. Average age of a family of 6 members is 22. If age of youngest member is 7 years then what was the average  age of family at birth of youngest member.

Solution: 7 years ago, Average age of family = 22-7=15 years.

But number of members = 6-1=5

So Average age = 15 + \frac{15}{5} = 18 years   Ans.

or,

Present age = 132

7 year ago = 132-7\times 6 = 90 years

At that time, number of members = 5

Therefore, average at that time = \frac{90}{5} = 18 Years.

6. Batting average of 40 innings of Dhoni was 50 runs. His highest score exceeded by lowest score by 172 runs. If there 2 innings are excluded, average of remaining 38 innings is 48. Find his highest score.

Solution:
HS-LS=172…………………..(1)

HS+LS=100+2 \times 38=176……………………(2)

from (1) & (2), we get

HS= 174   Ans.

Or,

Total runs in 40 inning= 40 \times 50 = 2000

Total runs in 38 inning = 38 \times 48 = 1824

2000 – 1824 = 176 (remaining inning)

let lowest score = x

then highest score = x + 172

x+x+172= 176

2x+172=176

2x = 4

x= 2

Therefore, Highest score = x +172 = 2 + 172 = 174

7. Average of marks of 5 students was 50. But later it was found that marks of a student were wrongly taken as 84 in place of 48. What will be the correct average?

Solution: Difference = 48-84 = -36 (extra)

Correct average = 50 – \frac{36}{5} = 42.8

8. Average of 11 results is 50. Average of first 6 results is 49 while that of last 6 results is 52. Find the 6th result.

Solution:

(294+312)-550=56 Ans.

9. Average weight of 3 persons A,B and C is 84 kg. If D joins them, average weight becomes 80 kg. If E whose weight is 3 kg more than D replaces A, then average weight of B,C,D and E becomes 79 kg. Find the weight of A in kg.

Solution:

E= 68+3=71 kg

\frac{B+C+68+71}{4}=79

B+C=177

A+B+C=3\times84=252

Therefore, A= 75  Ans.

10. Average of 5 consecutive odd numbers is 29, if next 3 odd numbers are also included, then find the new average.

Solution:

Surplus= 6 + 8+10 = 24 ( 6 comes from 35-29; 8 comes from 37-29 and 10 comes from 30-29)

New Average = 29+\frac{24}{8}=32 Ans.

 

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